Question

Which one of the following represents the specific speed of turbine?
1. NP^1/2/H^5/4
2. NQ^1/2/H^3/4
3. NQ^1/2/H^5/4
4. NP^1/2/H^3/4

Answer 1

Correct Answer - Option 1 : NP^1/2/H^5/4

Concept:

The specific speed of a turbine is defined as, the speed of a geometrically similar Turbine that would develop unit power when working under a unit head (1 m head). 

Is prescribed by the relation \({N_s} = \frac{{N\sqrt P }}{{{H^{\frac{5}{4}}}}}\)

• Low specific speed turbine: The specific speed is less than 50. (varying from 10 to 35 for single jet and up to 50 for a double jet) Example: Pelton wheel turbine
• Medium-specific turbine: The specific speed varies from 50 to 250. Example: Francis turbine
• High specific turbine: the specific speed is more than 250. Example: Kaplan or propeller turbine